A Comparison of Values for Initial and Residual Effectiveness of Rock Phosphates Measured In Pot and Field Experiments

Abstract

The effectiveness of Calciphos (500¦C calcined calcium-aluminium C-grade rock phosphate from Christmas Island), Queensland rock phosphate (low carbonate substituted apatite, from Duchess deposit, Northern Queensland [QRP]), and granular North Carolina rock phosphate (highly carbonate substituted apatite from U.S.A. [NCRP]) were compared with the effectiveness of monocalcium phosphate (MCP) fertilisers in pot and field experiments. Three different lateritic soils from south-western Australia and different plant species were used. In the pot experiment, the effectiveness of the fertilisers was measured relative to freshly applied MCP for 5 successive crops. Subterranean clover, oats, triticale..